The primary objectives of the proposed research are to quantify the formation rates of photooxidized plasmenylcholines and characterize their impact on membrane fluidity and lipidmediated membrane fusogenicity. An interdisciplinary project is proposed involving lipid synthesis, HPLC analysis with electrochemical & mass spectrometric detection, vesicle leakage, and EPR lipid diffusion experiments aimed at understanding the effects of photooxidation on membrane permeability. Water-soluble and membrane-soluble sensitizers, incorporated within guest membrane vesicles, will be illuminated under aerobic conditions to determine the effects of sensitizer localization on the lipid photooxidation rate. Results from these experiments will be compared with observations made using chemical oxidants. Labeled plasmenylcholines will be synthesized for 13C NMR experiments using methodology developed by Rui & Thompson [Chem. Eur. J. 1996 2 1505]. HPLC analysis and membrane fusion fluorescence assays will be used to monitor the rates of lipid photooxidation, vesicle lipid mixing, and vesicle contents mixing as a function of irradiation time & sensitizer type. Physical characterization of the membrane structures, before and after triggering, will also be performed using 31P NMR and EM techniques. These experiments will yield insights into the oxidative mechanisms of vinyl ether linked glycerophospholipids, such as plasmenylcholine and plasmenylethanolamine, that may be involved in reperfiision injury, multiple sclerosis, and other demyelinating disorders.